A standard drill chuck such as used in a hammer drill and as disclosed in U.S. Pat. No. 5,765,839 has a body provided centered on an axis with an annular array of ratchet teeth and a plurality of jaws radially displaceable relative to the body between inner and outer positions. To this end the body is formed with guides angularly equispaced about the axis, open at front and rear ends at front and rear faces of the chuck body, and also opening at windows on the side of the body where teeth on the outer edges of the jaws are exposed. A tightening ring is axially fixed but rotatable about the axis on the body in a tightening direction and in an opposite loosening direction and an internal screwthread on the tightening ring engages the teeth of the jaws to move them radially together and axially forward on rotation of the tightening ring in the tightening direction and radially apart and axially rearward on rotation of the tightening ring in the loosening direction.
A locking element engageable with the teeth and angularly fixed on the tightening ring is radially displaceable between a locking position engaging the ratchet teeth and preventing rotation of the body in the loosening direction and a freeing position permitting free rotation of the body relative to the tightening ring. A setting ring angularly displaceable on the tightening ring is formed with a pair of angularly spaced and radially open seats. A pair of angularly spaced abutments between the setting ring and the tightening ring limit angular movement of the sleeve on the ring. A cam on the setting ring is engageable with the locking element for displacing the locking element into the locking position when the setting ring is in one of its end positions and for displacing the locking element into the freeing position when the setting ring is in the other of its end positions. This locking system, which has proven successful in very large production runs on the market, allows an outwardly directed force to be applied to the tightening sleeve, which force requires the tightening sleeve to be supported radially on the chuck body in order to ensure optimal concentricity.
DE 20 2005 016 952 discloses a closure disk that braces the tightening sleeve against the chuck body and also braces the tightening sleeve on the chuck body at the rear face of the drill chuck.
U.S. Pat. Nos. 5,882,153 and 5,927,914 discloses a so-called short drill chuck in which the jaws exit project from the guide seats when these jaws are adjusted to wider tool-shank diameters, and project beyond the rear face of the chuck body when in their extreme position. The parts of the jaws the project beyond the rear face of the chuck body are accommodated here by the spindle housing of a drive unit that can be attached to the drive-spindle seat.
In the case of short drill chucks that include a locking unit, however, the guide configuration of the jaws makes it impossible to mount a closure disk at the rear face of the chuck body so as to guide the tightening sleeve thereon since this closure disk must have through-holes so as to ensure that the jaws can project beyond the rear face of the chuck body. The problem is thus often found in these drill chucks that concentricity is impaired, and this results in reduced service life and unwanted vibrations.